Lubricant composition



United States Pate LUBRICANT COMPOSITION Warren Lowe, Berkeley, and William T. Stewart, El Cerrito, Calif., assignors to California Research Corporation, San Francisco, Calif., a corporation of Delaware No Drawing. Application December 29, 1955,

Serial No. 556,086

13 Claims. (Cl. 25233.4)

This invention relates to, a novel lubricant composition. More particularly, the invention is concerned with a new and, unusually effective lubricating oil composition having improved corrosion inhibiting properties.

Lubricating oils generally have a tendency to become corrosive to metals during their normal service due to oxidation and the formation of decomposition products. Modern internal combustion engines in particular are operated under conditions which involve increased temperature changes, higher speeds and reduced clearances, all of which conditions aggravate the formation of corrosive decomposition products and accentuate the need for improved lubricating ability in the lubricant composition. Furthermore, these engines commonly employ alloy metal bearings which, besides their possible catalytic effect on the decomposition of lubricating oils, are especially subject to corrosive attack and alteration of their friction characteristics which places a greater burden on the lubricity of the lubricant composition.

Corrosion inhibitors which have been added heretofore to lubricating oils in general to improve their resistance to the formation and effect of corrosive products have not been entirely satisfactory. Many of the additives are only partly effective and permit the bearings and other metal surfaces to be slowly but eventually corroded away. Other additives which are substantially effective at the outset are used up during service and are therefore active only for a limited period.

Another, more specific disadvantage of the corrosion inhibitors employed prior to this has been due to the fact that'lubricating oils for internal combustion engines are commonly compounded with additives such as wear inhibitors, pour point depressants, sludge inhibitors, detergents and the like to loosen, suspend 'and otherwise counteract the eifect of decomposition products and'provide efficient lubrication. Unfortunately, many of these agents adversely afliect the activity of the corrosion in- .hibitors, and it is necessary to find inhibitors which will function in combination with them.

Furthermore, many of the most efiective corrosion inhibitors known prior to this invention contain active sul fur in some form and-are therefore undesirable for use with silver and similar metal-containing bearings which are subject to attack by active :sulfur. These types of bearings, although once not so widely used and therefore considered to constitute only a minor problem, are being increasingly employed today. Particularly incertain'important classes of internal combustion engines, as, for example, marine and railroad diesel engines, silver metal containing bearings are" more and more common, and the problem of providing proper lubrication for them from the standpoint .of low corrosivity and impro'ved'lubricity is one of major importance. 1 T

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In accordance with the present invention, a superior inhibiting properties has been found comprising a major portion of an oil of lubricating viscosity corrosive to metal surfaces in normal use and a minor portion, sulficient to inhibit corrosion, of' a member of the group consisting of ammonium isophthalate, ammonium terephthalate, isophthalamide, terephthalamide and N-alkyl ammonium isophthalates, N-alkyl ammonium terephthalates, N-alkyl isophthalamides and N-alkyl terephthalamides in which the alkyl groups contain a total of 8 to 30 carbon atoms.

The novel lubricant composition according to the in.- vention is characterized by remarkable corrosion inhibit ing properties for metal surfaces and alloy bearings over extended periods of operation. It also provides a greatly improved quality of lubrication for bearings and other rubbing surfaces. A further outstanding characteristic of the composition lies in the fact that these beneficial properties are obtained without adverse eifect from other conventional additives commonly employed in lubricant compositions. Still another advantage of the lubricant composition according to the invention is its ability to provide unusually effective lubrication for particular alloy bearings such as the silver metal-containing bearings more and more commonly found in marine and railroad diesel engines. p

In a more specific and preferred embodiment the present invention is concerned with a lubricant composition comprising an oil of lubricating viscosity in combination with a lubricating oil detergent additive, said combination being corrosive to metal surfaces in normal use, and a minor portion, suflicient to inhibit corrosion, of a member of the group consisting of ammonium isophthalate, ammonium terephthalate, isophthalamide, telephthalamide and N- alkyl ammonium isophthalates, N-alkyl ammonium terephthalates, N-alkyl isophthalamides and N-alkyl terephthalamides in which the'alkyl groups contain a total of 8 to 30 carbon atoms, said minor portion of lubricating oil detergent additive being sufficient to suspend said member in the oil of lubricating viscosity.

The lubricating oil detergent additive of the composition is a well-known type of additive generally used in lubricant compositions. The term, as employed here in its commonly accepted sense, denotes a recognized class of chemical compounds which are known for their function of enabling a lubricating oil medium to maintain oxidationproducts, resins, and other types of insoluble materials in suspension or dispersion in the oil. Such detergent compounds in lubricant compositions in actual use may remove naturally formed protective films from metal surfaces, thus rendering the compositions more corrosive. Illustrative lubricating oil detergent additives fall within general classes of types. Examples of the better known classes are the metal salts of naphthenic acids such as aluminum naphthenate; metal salts of fatty acids and substituted fatty acids such as calcium stearate, calcium phenyl stearate, basic calcium phenyl stearate and calcium dichlo'rostearate; metal salts of aromatic acids and substituted aromatic acids such as calcium octyl salicylate and basic calcium octyl salicylate; metal salts of petroleum sulfonic acids such as calcium sulfonate and basic calcium sulfonate; metal salts of alkyl phenol sulfides such as barium amylphenol sulfide; metal salts of alkyl phenols such as aluminum dicetyl phenate and calcium dicetyl phenate; metal salts of thiophosphoric acid esters such as the zinc salt of the p-tert. amylphenyl ester of dithiophosphoric acid; and metal salts of wax substituted phenol derivatives such as the wax substituted metal phenates. Presently preferred are the alkaline earth metal petroleum sulfonates and alkaline earth metal phenates such as basic calcium petroleum sulfonate, calcium cetyl phenate and sulfurized calcium cetyl phenate. These particular lubricating oil deter'gent additives, alone and together, are found to be unusually effective when combined with the ammonium salts and amides of isophthalic and terephthalic acid in lubricant compositions for internal combustion engine use according to this invention.

Nonmetallic lubricating-oil detergent additives are also suitable for the lubricant compositions of the invention. This type of lubricating oil detergent additive for present purposes, may be conveniently described as a macromolecular copolymer characterized by oil solubilizing monomer groups and polar-type monomer groups which apparently provide the detergent effect. The oil solubiliziug monomer which is well known in the field of polymeric lubricating oil viscosity index improvers may be an olefin such as hexadecene-l or octyl styrene; an ester such as allyl stearate or lauryl methacrylate; an ether such as vinyl n-butyl ether; or a ketone such as methallyl isobutyl ketone. The polar type monomer group may be an unsaturated monocarboxylic acid such as methacrylic acid, amides and esters thereof such as n-lauryl acrylamide and pentaerythritol monomethacrylate, unsaturated dicarboxylic acids such as maleic acid and amides and esters thereof such as the half-amides, half-esters, diamides and diesters as illustrated by the N-N-di-tert.butyl monoamide of maleic acid, monopentaerythritol ester of maleic acid and similar diamides and diesters.

Other oil-soluble dispersants may be included in the lubricant compositions either in addition to or in lieu of the metallic and nonmetallic lubricating oil detergent additives described above. Such dispersants are illustrated by the phosphatides such as animal lecithin and the partial or complete esters of long-chain carboxylic acids with polyhydric alcohols such as pentaerythritol mono-oleate and glycerol sorbitan laurate. These materials, like the other dispersants or lubricating oil detergent additives mentioned previously, also serve to maintain the ammonium salts and amides of isophthalic or terephthalic acid of the present compositions in stable suspension. Thus, the salts or amides are circulated freely in the lubricating oil system wherever corrodible metal surfaces are encountered to effectively inhibit corrosion and promote improved lubrication of rubbing surfaces.

The ammonium salts and amides of isophthalic acid and terephthalic acid are commercially available and readily obtainable from the acids themselves by conven- IVhOCOCOM: COM:

Ammonium salts and amides Ammonium salts and amides i terephthalic acid of isophthalic acid wherein M1 and M2, which may be the same or different, are ammoniumoxy (-ONH4) and amido (--NH2) groups and N-alkyl ammoniumoxy I'll (-0H-IIIR1, sometimes referred to as amlnehydroxy) and groups wherein R1, R2 and R3, which may be the same or different, are hydrogen or alkyl groups, at least one being an alkyl group, said alkyl groups containing a total of 8 to 30 carbon atoms. These particular salts and amides, it will be noted, are unlike those of other dicarboxylic acids in that the carbonyl-containing groups are located where they will be able to function most effectively. The salts and amides of other dicarboxylic acids of both aliphatic and aromatic types may cyclize and from their imides which may not be as effective as the salts or amides.

The ammonium salts and amides of isophthalic acid and terephthalic acid may be employed together in-lubrieating oil compositions according to the invention. This may be advantageous where conditions of operation are such that the solubility of the salt or amide of isophthalic acid or terephthalic acid becomes critical. In a case of this type, the lubricating oil composition may be saturated with salts or amides of one of the acids and still be capable of incorporating a similar amount of the salt or amide of the other acid to augment the corrosion inhibiting properties. The compositions of this invention containing the ammonium salts and amides of isophthalic and terephthalic acid, as described above, are surprisingly more effective in the inhibition of corrosion of metal surfaces such as alloy metal bearings and the like than similar compositions containing their isomers and analogues of the orthophthalic acid type, commonly referred to in the art as phthalic acid. Still more unexpected is the fact that ammonium salts of isophthalic acid appear to be substantially better corrosion inhibitors than the corresponding salts of terephthalic acid. So far as is known, it has never been suggested heretofore that any of these particular salts or amides might be effective in lubricant compositions as corrosion'inhibitors, let along that isophthalic would be substantially superior to their terephthalic isomers in such a capacity.

In accordance with a preferred embodiment of the invention, as already described, a lubricating oil detergent additive is present in a minor amount, sufiicient to suspend the salts or amides in the oil of lubricating viscosity. Amounts up to 20% by weightof the lubricantcomposition are generally suitable for this purpose, although concentrates for use in blending operations to prepare the lubricant compositions of the invention may contain up to 50% by weight or more of the detergent. For present purposes, very superior lubricant compositions .are obtained with from 0.1 to 10% by weight of the detergent.

The ammonium salts or amides of isophthalic acid and terephthalic acid are present in the lubricant composition in a minor portion, sufficient to inhibit corrosion, as stated above. Generally, amounts up to about 1.0% by weight of the lubricant composition are very satisfactory. For present purposes the preferred lubricant compositions contain from about 0.001 to 0.5% by weight. Such compositions are unusually stable and provide remarkably effective corrosion inhibition for extended periods.

Any of the well-known types of oils of lubricating viscosity are suitable base oils for the compositions .of the invention. In normal usage these oils are corrosive to metal surfaces. They include hydrocarbon or mineral lubricating oils or naphthenic, parafiinic, and mixed naphthenic and parafi'lnic types. They may be refined by any of the conventional methods such as solvent refining and acid refining. Synthetic hydrocarbon oils of the alkylene polymer type or those derived from coal and shale may also be employed. Alkylene oxide polymers and their derivatives such as the propylene oxide polymers and their ethyl esters and acetyl derivatives in which the terminal hydroxyl groups have been modified are also suitable. Synthetic oils of the dicarboxylic acid estertype including dibutylv adipate, di-Z-ethylhexyl sebacate, di-n-hexyl fum'arate polymer, di-lauryl acylate, and thelik'e maybe used. Alkyl benzene types'ot synthetic oils such as tetradecyl benzene, etc., are also included. Liquid esters of acids of phosphorus including tricresyl phosphate, diethyl esters of decane phosphonic acid, and the like may also be employed. Also suitable are the polysiloxane oils of the type of polyalkyl-, polyaryl-, polyalkoxyand polyaryloxy siloxanes such "as polymethyl siloxane, polymethylphenyl siloxane and polymethoxyphenoxy siloxane and silicate ester oils such as tetraalkyland tetraaryl silicates of the tetra-Z-ethylhexyl silicate and tetra-p-tert.-butylphenyl silicate types. f

As already mentioned, the corrosion inhibiting compositions of this invention are outstanding in that they are unusually effective in the form of compounded lubricating oils containing conventional additives such as oxidation inhibitors, detergents or dispersants, sludge inhibitors, pour depressants, VI improvers, antifoaming agents, rust inhibitors, oiliness or film strengthening agents, wear inhibitors, dyes and the like. A great many of these compounded oils are generally corrosive to metal surfaces and alloy metal bearings in particular, and it is an exceptional attribute of the present composition wherebyycorrosion inhibited compounded lubricating oils are provided.- A further very desirable feature of the compositions according to the invention is the fact that the corrosion inhibition is obtained without any noticeable adverse efiect on the other additives, thus permitting more efficient all-around lubrication of internal combustion engines and other types of machines where unusually severe conditions of service are more and more commonly encountered.

Mineral lubricating oils are preferred in the compounded lubricating oil compositions of the invention since such oils as generally compounded for internal combustion engine use are unusually corrosive to metal surfaces and are thus most greatly benefited by the addition of the particular phthalic acids. p

The following examples are submitted as additional illustrations of the invention. These examples show the preparation of the various lubricant compositions and the evaluation of their eifectiveness as corrosion inhibitors. The proportions given in these examples, unless otherwise specified, are on a weight basis and include both percent (percent) and millimoles per kilogram (mM./l g.) of the various additives.

EXAMPLE 7 I alcohol. The mixture was stirred at 170 F. until all of the isophthalic acid was dissolved. 12.9 parts of 2- ethylhexyl amine dissolved in about 90 parts of benzene wasthen added to the solution. The contents of the reaction vessel were stirred for two hours at 170 to 180 F. Following this, the benzene and isopropyl alcohol were permitted to distill off under reduced pressure. The residue'was stirred at 190 F. for 30 minutes. Theprodnot 'was mono(2-ethylhexyl ammoniumfisophthalate. It was a brown,viscous liquid soluble in mineral oil.

' EXAMPLE 1r- 7 In this example, di(2-ethylhexyl ammonium) isophthalate was prepared bymodifying the procedure of the above example so as to react 25.8 parts of Z-ethylhexyl amine with the isophthalic acid. The product was a brown, viscous, liquid material soluble in mineral oil.

p EXAMPLE III 3.32 parts of crude isophthalic acid (85% isophthalic and 15% terephthalic acid) and 300 parts of isopropyl alcohol were charged "to a reaction vessel equipped with stirrer, condenser and heating means. The mixture was stirred at 170 F. until all of the isophthalic acid was dissolved; To the solution was then added 21 parts of dioctadecyl amine dissolved in about parts of benzene. After stirring the reactants at to F. for about two hours, the benzene and isopropyl alcohol were dissolved oft under reduced pressure. The residue was then stirred at F. for an additional 30 minutes. The product thus obtained was di(dioctadecyl ammonium) isophthalate. It was a brown, viscous liquid soluble in mineral oil.

EXAMPLE IV To a reaction vessel were charged 1.66 parts of terephthalic acid and 1000 parts of isopropyl alcohol. The reaction vessel was equipped with stirring and heating means and a water condenser. The contents were stirred at 170 F. until all of the terephthalic acid was dissolved. 10.5 'parts of dioctadecyl amine dissolved in about 90 parts of benzene was then added to the solution. The stirring was continued for two hours at a temperature of about 170 to 175 F. The benzene and isopropyl alcohol were then permitted to distill off under reduced pressure, and the residue in the reaction vessel was stirred at about 190 F. for 30 minutes longer. The product was di(dioctadecyl ammonium)terephthalate. It was a brownish, viscous material soluble in mineral oil.

A number of corrosion-inhibited lubricating oil compositions containing representative ammonium salts and amides of isoand terephthalic acids as the corrosion inhibitor were prepared according to the'procedures illustrated by the above examples. 'Several difierent compositions exemplifying various types of corrosion inhibitors according to the invention and their eifectiveness in standard lubricating oil tests for determining corrosion inhibition are listed in the following tables.

In the copper-lead strip corrosion test, a polished copper lead strip is weighed and immersed in 300 ml. of test oil contained in a 400 ml. lipless Berzelius beaker. The test oil is maintained at 340 F. under a pressure of 1 atmosphere of air and stirred with the mechanical stirrer at 1000 R. P. M. After 2 hours, a synthetic naphthenate catalyst is added to provide the following catalytic metals:

The test is continued for 20 hours. The copper-lead strip is then removed, rubbed vigorously with a soft cloth and weighed to determine the net weight loss. I

The lubricating oil compositions in the tests include a variety of base oils. Mineral oil (A) is an acid refined white mineral oil. Synthetic oil (B) is a poly-1,2-propylene glycol phenyl methyl diether having a molecular weight of 1200. Synthetic oil (C) is di-2-ethylhexyl sebacate. compounded oil (D) is a solvent refined SAE 40 mineral lubricating oil having a viscosity index of 60 and containing 10 mM./kg. of basic calcium petroleum sulfonate and 20 mM./kg. of sulfurized basic calcium cetyl phenate. Compounded oil (E) is the same mineral lubricating oil', but contains only 10 mM./kg. basic calcium petroleum sulfonate. compounded oil (F) is an acid refined white mineral oil containing 10% by weight of a.

copolymeric detergent which is the copolymer of'lauryl methacrylate with the diethylaminoethyl ester of acrylic acid sold by Du Pont as Lubricating Oil Additive No. 5 65 Illustrative test results are 'shown in the following table. The concentrations of the ammonium salts and amides of isophthalic acid and terephthalic acid employed are given in percent by weight of the composition.

Table COPPER-LEAD STRIP CORROSION TEST Copper-Lead Additive and Oil Strip Weight Loss (Mg.)

N onel\flineral Oil (A) 66. 2 O.3(;1%11&)1(octadeoy1 ammonium) isophthalate in mineral o 0. 7 N one-Synthetic oil (B) 4. 4 0.30% D1(octadecyl ammonium) isophthalate in synthetic oil (B) 1.0 None-Synthetic oil 46. 8 0.301%,(3Koctadecyl ammonium sophthalate o 30. 1 None-compounded oil (D). 250-300 0.02% D ammonium isophthalate in compounded oil (D). 11. 1 0.00% D ammomum isophthalate in compounded oil (D). 10. 0 0.1% D1(2-ethylhexy1 ammonium) isophthalate in compounded oil (D) 62. 3

0.2% Di(octadecyl ammonium)isophthalate in compounded o1l (D) 7. 5 0.2% Mono(1sooctadecyl ammonium)isophthalate in compounded oil (D) 20. 9 0.15% Mono(n-octadecyl ammonium)isophthalate in compounded oil (D) 26. 3 0.15% D1(n-octadecyl ammonium)isophthalatc in compounded oil (D) 11.7 0.15% Di(dioctadecyl ammonium)isophthalate in compounded oil (D 24. 0 0.2% lgono(n-octadeoyl)m-phthalamide in compounded 01 27. 4 0.2%, (rfiono-m-phthalamide (half amide) in compounded 42.0 0.58%, (DRKn-octadeoyDm hthalamide compounded 42. 9 0.2% Di(n-octadecyl ammonium)terephthalate in compounded oil (D) 37.3 0.2% Mono(n-octadecyl ammonium)terephthalate in compounded oil (D) 21.1

0.3% Mono(dioc tadccyl ammonium)terephtha1ate in I compounded 011 (D) 7.0 0.15% D1(d1octadecyl ammonium)terephthalate in compounded oil D 12. 4 N one-Compounded oil (E) 272. 4 0.30% D1( i-ootadecyl ammoniurnfisophthalate in com pounded oil (E) 15. 0 NoneOompounded oil (F) 158. 6 0.15% Isophthalic acid diarnide in compounded oil (F)... 36. 5

The test results shown in the above table illustrate the efiectiveness of the lubricant compositions according to this invention under low temperature operating conditions. Copper-lead corrosion is substantially inhibited in all of the lubricant compositions containing the ammonium salts and amides of isophthalic acid or terephthalic acid. The test results show further that the corrosivity of compounded lubricating oils, which are much more corrosive than the base oil alone, is effectively inhibited. As previously mentioned, the inhibition of corrosion in such compounded lubricant compositions constitutes a preferred embodiment of the invention.

Although the compositions of the invention have been described above primarily as internal combustionengine lubricants, they are also suitable for other applications. Such applications include their use as gear lubricants, ice machine oils, instrument oils, constituent oils for grease manufacture, turbine oils, and the like.

This application is a continuation-in-part of Warren Lowe and William T. Stewart U. S. patent application Serial No. 478,517, filed December 29, 1954, now abandoned.

We claim:

1. A lubricant composition comprising a major portion of an oil of lubricating viscosity corrosive to metal surfaces in normal use and a minor portion up to 1.0% by weight of the lubricant composition, sufiicient to inhibit corrosion, of a member of the group consisting of ammonium isophthalate, ammonium terephthalate, isophthalamide, terephthalamide and N-alkyl ammonium isophthalates, N-alkyl ammonium terephthalates, N-alkyl isophthalamides and N-alkyl terephthalamides in which the alkyl groups contain a total of 8 to 30 carbon atoms.

2. A lubricant composition comprising a major portion of a mineral lubricating oil corrosive to metal surfaces in a normal use and a minor portion up to 1.0% by weight of the lubricant composition, sufiicient to inhibit corrosion, of a member of the group consisting of ammonium isophthalate, ammonium 'terephthalate, iso

g phthalamide, terephthalamide and N-alkyl ammonium isophthalates, N-alkyl ammonium terephthalates, N-alkyl isophthalamides and N-alkyl terephthalamides in which the alkyl groups contain a total of 8 to 30 carbon atoms. 7 3. A lubricant composition comprising a major portion of an oil of'lubricating viscosity in combination with a minor portion of a lubricating oil detergent additive, said combination being corrosive to metal surfaces in normal use and a minor portion, sufiicient to inhibit corrosion, of a member of the group consisting of ammonium isophthalate, amomnium terephthalate, isophthalamide, terephthalamide and N-alkyl ammonium isophthalates, N-alkyl ammonium terephthalates, N-alkyl isophthalamides and N- alkyl terephthalamides in which the alkyl groups contain a total of 8 to 30 carbon atoms, said minor portion of lubricating oil detergent additive being sufiicient to suspend said member in the oil of lubricating viscosity.

4. A lubricant comprising a major portion of a mineral lubricating oil in combination with a minor portion of a lubricating oil detergent additive, said combination being corrosive to metal surfaces in normal use and a minor portion, sufficient to inhibit corrosion, of a member of the group consisting of ammonium isophthalate, ammonium terephthalate, isophthalamide, terephthalamide and N-alkyl ammonium isophthalates, N-alkyl ammonium terephthalates, N-alkyl isophthalamides and N-alkyl terephthalamides in which the alkyl groups contain a total of 8 to 30 carbon atoms, said minor portion of lubricating oil detergent additive being sufficient to suspend said member in the mineral lubricating oil.

5. A lubricant composition comprising a major portion of a mineral lubricating oil in combination with a minor portion of an alkaline earth metal petroleum snlfonate, said combination being corrosive to metal surfaces in normal use and a minor portion, suflicient to inhibit corrosion, of diammonium isophthalate, said minor portion of alkaline earth metal petroleum snlfonate being sufficient to suspend said isophthalate in the mineral lubricatin oil.

6. A lubricant composition comprising a major portion of a mineral lubricating oil in combination with a minor portion of an alkaline earth metal petroleumsulfonate, said combination being corrosive to metal surfaces in normal use and a minor portion, sufiicient to inhibit corrosion, of di(octadecyl ammonium) isophthalate, said minor portion of alkaline earth metal petroleum snlfonate being sufiicient to suspend said isophthalate 1n the mineral lubricating oil.

7. A lubricant composition comprising a ma or portlon of a mineral lubrication oil in combination with a minor portion of an alkaline earth metal petroleum snlfonate, said combination being corrosive to metal surfaces 1n normal use and a minor portion, suificient to inhibit corrosion, of mono(dioctadecy1 ammonium) terephthalate, said minor portion of alkaline earth metal petroleum snlfonate being sufficient to suspend said terephthalate in the mineral lubricating oil.

8. A lubricant composition comprising a major portion of a mineral lubricating oil in combination with a minor portion of an alkaline earth metal petroleum snlfonate and an alkaline earth metal alkyl phenate, said combination being corrosive to metal surfaces in normal use and a minor portion, sufficient to inhibit corrosion, of diammonium isophthalate, said minor portion of alkaline earth metal petroleum snlfonate and alkaline earth metal alkyl phenate being suificient to suspend said isophthalate in the mineral lubricating oil.

9. A lubricant composition comprising a major portion of a mineral lubricating oil in combination with a minor portion of an alkaline earth metal petroleum sulfonate and an alkaline earth metal alkyl phenate, said combination being corrosive to metal surfaces in normal use and a minor portion, sufiicient to inhibit corrosion, of di(octadecyl ammonium) isophthalate, said minor porion of alkaline earth metal petroleum snlfonate and alkaline earth metal alkyl phenate being suflicient to suspend said isophthalate in the mineral lubricating oil.

10. A lubricant composition comprising a major portion of a mineral lubricating oil in combination with a minor portion of an alkaline earth metal petroleum sulfonate and an alkaline earth metal alkyl phenate, said combination being corrosive to metal surfaces in normal use and a minor portion, suflicient to inhibit corrosion, of mono(dioctadecyl ammonium) terephthalate, said minor portion of alkaline earth metal petroleum sulfonate and alkaline earth metal alkyl phenate being sufficient to suspend said terephthalate in the mineral lubrieating oil. a

11. A lubricant composition comprising a major portion of a mineral lubricating oil in combination with a minor portion of a calcium petroleum sulfonate, said combination being corrosive to metal surfaces in normal use and a minor portion, suflicient to inhibit corrosion, of diammonium isophthalate, said minor portion of calcium petroleum sulfonate being suflicient to suspend said isophthalate in the mineral lubricating oil.

12. A lubricant composition comprising a major portion of a mineral lubricating oil in combination with a minor portion of a calcium petroleum sulfonate, said combination being corrosive to metal surfaces in normal use and a minor portion, sufficient to inhibit corrosion,

- of di(octadecyl ammonium) isophthalate, said minor portion of calcium petroleum sulfonate being suflicient to suspend said isophthalate in the mineral lubricating oil.

13. A lubricant composition comprising a major portion of a mineral lubricating oil in combination with a minor portion of a calcium petroleum sulfonate, said combination being corrosive to metal surfaces in normal use and a minor portion, sufiicient to inhibit corrosion, of mono- (dioctadecyl ammonium) terephthalate, said minor portion of calcium petroleum sulfonate being sufiicient to suspend said terephthalate in the mineral lubricating oil.

References Cited in the file of this patent UNITED STATES PATENTS 2,134,736 Renter Nov. 1, 1938 2,158,096 Werntz May 16, 1939 2,280,474, Byrkit Apr. 21, 1941 2,595,169 Rudel Apr. 29, 1952 

1. A LUBRICANT COMPOSITION COMPRISING A MAJOR PORTION OF AN OIL OF LUBRICATING VISCOSITY CORROSIVE TO METAL SURFACES IN NORMAL USE AND A MINOR PORTION UP TO 1.0% BY WEIGHT OF THE LUBRICANT COMPOSTITION, SUFFICIENT TO INHIBIT CORROSION, OF MEMBER OF THE GROUP CONSISTING OF AMINOMIUM ISOPHTHALATE, AMMONIUM TEREHTHALATE, ISOPHTHALAMIDE, TEREPHTHALAMIDE AND N-ALKL AMMONIUM ISOPHTHALATES, N-ALKYL AMMONIUM TEREPHTHALATES, N-ALKYL ISOPHTHALAMIDES AND N-ALKYL TEREPHTHALAMIDES IN WHICH THE ALKYL GROUPS CONTAIN A TOTAL OF 8 TO 30 CARBON ATOMS. 